There has been industrial demand for production of colored prints of gradated density distribution. To satisfy this demand, at least one halftone dot film of gradated density distribution must be provided for each of the color separations Y (Yellow), K (Black), C (Cyan) and M (Magenta) of a print. In producing such halftone dot film, a monochrome film of a gradated density distribution (a gradation master) has been used.
More precisely, an image signal obtained by scanning a gradation master provided as an original is exposed to a color correction process to be used for producing a mono-color halftone dot film of gradated density distribution. Then, a print of a desired color or density distribution is obtained by using such films produced for no fewer than two of the color separations Y, K, C and M.
However, because this method is applicable only to density gradation of one (lengthwise or sidewise) direction of a recording film, restricted by the gradation master, the method cannot be applied to form a density distribution pattern such as a concentric circle. In addition, the method is inconvenient because, using it, the degree of density gradation cannot be freely adjusted.
Therefore, a print of only a limited color or density gradation pattern can be obtained by any combination of halftone dot films of Y, K, C and M in the prior art.